Unable to perform alpha surface reconstruction on Apple Silicon

[Piflyer]

Checklist

• I have searched for similar issues.
• For Python issues, I have tested with the latest development wheel.
• I have checked the release documentation and the latest documentation (for master branch).

Describe the issue

I am trying to run alpha surface reconstruction on my M2 Max Macbook Pro, but it keeps on crashing. I am currently using a Conda environment that is configured for ARM. I am currently using Open3D version 17.0 and it is installed from pip.

Steps to reproduce the bug

import open3d as o3d
armadillo_mesh = o3d.data.ArmadilloMesh()
mesh = o3d.io.read_triangle_mesh(armadillo_mesh.path)
pcd = mesh.sample_points_poisson_disk(900)
alpha = 0.03
mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_alpha_shape(pcd, alpha)

Error message

[Open3D WARNING] Creating from empty legacy TriangleMesh.
libc++abi: terminating with uncaught exception of type std::out_of_range: unordered_map::at: key not found

Expected behavior

Being able to successfully do alpha reconstruction

Open3D, Python and System information

- Operating system: macOS 13.2.1
- Python version: Python 3.10.0
- Open3D version: 0.17
- System architecture: arm64 / apple-silicon
- Is this a remote workstation?: no
- How did you install Open3D?: pip

Additional information

No response

[yosho27]

Reproduced with a slightly different error message

- Operating system: Windows 10 Pro
- Python version: Python 3.9.13
- Open3D version: 0.18.0
- System architecture: x64-based PC
- Is this a remote workstation?: no
- How did you install Open3D?: pip

[Open3D WARNING] Creating from empty legacy TriangleMesh.

IndexError: invalid unordered_map<K, T> key

Additionally, this can be reproduced with a point cloud at least as small as 6 points
[[4,1,0],[0,0,0],[2,0,0],[0,0,1],[3,1,1],[-2,0,1]] and alpha=1

[hsellik]

 - Operating system: macOS Sonoma Version 14.2.1 
 - Python version: Python 3.9.18
 - Open3D version: 0.18.0
 - System architecture: arm64 / apple-silicon / M3
 - Is this a remote workstation?: no
 - How did you install Open3D?: pip

Encountering the same issue on M3 Mac.

[kongbai-account]

• Operating system: win10
• Python version: Python 3.8.0
• Open3D version: 0.18.0
• System architecture: x64-based PC
• Is this a remote workstation?: no
• How did you install Open3D?: pip

[Open3D WARNING] [CreateFromPointCloudAlphaShape] invalid tetra in TetraMesh
[Open3D WARNING] Creating from empty legacy TriangleMesh.
IndexError: invalid unordered_map<K, T> key

[rxba]

This is a point scale issue, i.e. max_bound (Armadillo) is [62.1 96.4 56.8] and max_bound (Bunny) is [0.061 0.187 0.058]. If the alpha is large enough (e.g. 10), or you scale down the Armadillo, it works again.

The unordered_map key error is caused when the reconstructed mesh becomes empty internally, e.g. because of the aforementioned scale issue. This is a bug and I've opened a PR to fix the error, warn the user and return the empty mesh instead.